a) Field of the Invention
The invention is directed to an arrangement for machining workpieces by means of a laser, particularly for cutting, perforating, notching, engraving, drilling and inscribing workpieces with three-dimensional structures of different sizes. It can also be used advantageously for removing layers from such workpieces.
b) Description of the Prior Art
Arrangements for machining a workpiece by means of a laser basically comprise a laser, a device for guiding the laser beam to the workpiece and a device for holding the workpiece. For processes in which a relative movement (forward feed) must be carried out between the laser beam, as tool, and the workpiece (e.g., cutting, perforating, ablating), this relative movement is usually realized by the device for guiding the laser beam, while the workpiece is held so as to be stationary.
Various basic principles are known for such devices for guiding the laser beam to the stationary workpiece surface.
For machining of large-area workpieces in particular, arrangements are known in which a laser head focusing the laser beam can be moved freely in a parallel to the workpiece surface by means of an overhead gantry or frame. The laser beam travels from the laser to the laser head by way of an articulated mirror arm. This is advantageous in that, when suitably dimensioned, a frame of this kind can guide the laser beam also over very large workpiece surfaces. Its disadvantages consists in a large space requirement, limited machining speed, particularly when the machining direction is changed often, and the fact that it is applicable exclusively on plane workpiece surfaces.
Arrangements in which a laser head is arranged at a robot arm which is freely movable in three dimensions are also known for machining large workpiece surfaces. In this case also, the laser beam, is guided to the laser head by an articulated mirror arm. The size of the workpiece surface to be machined is limited only by the free space for the movement of the robot arm and mirror articulation arm. The inertia of the mechanics of the robot arm and of the articulated mirror arm also allow only a limited machining speed.
In both solutions, it is known to arrange at the laser head a gas nozzle through which a flow of gas is directed to the surface to be machined in order to prevent flames which lead to unwanted soot deposits and to prevent depositing of melted material. Since the laser radiation exits the laser head in a fixedly defined direction and is guided over the workpiece surface at a defined distance, the gas nozzle is mounted on the laser head at a fixed angle to the laser beam such that the laser beam and the gas jet exiting from the gas nozzle are always directed to the same point on the workpiece surface.
It is known to use optical beam deflecting units, also known as laser scanners, for machining small, plane surfaces. The beam is guided by the tilting of mirrors. This is advantageous because of the high speed that can be achieved and due to the accurate precision of the beam deflection. It is disadvantageous that the laser beam can only sweep over a small spatial area. A combination of such arrangements with a gas feed to the machining location is not known.
Therefore, the only solutions used in the prior art for arrangements in which workpieces with large surfaces extending in three dimensions are to be machined are those in which the laser beam is guided along the desired machining line on the workpiece surface by means of an articulated mirror arm fastened to a robot arm.
It is the primary object of the invention to provide an arrangement for machining workpiece surfaces extending in three dimensions in which a flow of gas is directed to the machining location and which permits a faster machining speed compared to conventional arrangements independent of the extent and shape of the machining line.
This object is met for an arrangement according to the invention, the arrangement being for machining workpiece surfaces extending in three dimensions by a laser comprising a stationary laser, an articulated mirror arm, a robot arm connected to a robot for guiding the second end of the articulated mirror arm, a holding device for fixing a workpiece, at least one gas nozzle by which a flow of gas is directed to the workpiece surface and a control device for controlling the robot arm, and in that a laser scanner is fastened to the robot arm and is connected to the articulated mirror arm in such a way that the beam exiting from the second end of the articulated mirror arm is coupled into the laser scanner and the gas nozzles are arranged at the laser scanner so as to be movable in such a way that they can be oriented to the workpiece surface by a gas nozzle propulsion communicating with the control device, so that the gas flow and the radiation exiting from the laser scanner via an exit face coincide at a point on the workpiece surface.
The invention will be described more fully in the following in an embodiment example with reference to a drawing.